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Author Topic: 24v vs. 12v  (Read 7080 times)
phil4501
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« on: May 20, 2006, 07:15:04 AM »

I can certainly understand why one would keep 24v if they already have it. I can also see that switching to 12v has worked out well for alot of folks. Has anyone been serious enough about thier preference to take a coach that was 12v and switch it to 24v?
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« Reply #1 on: May 21, 2006, 05:07:34 AM »

Greetings Phil,

When you say switch the coach to 12v from 24, do you mean, everything? or  just the headlamps, & marker lamps? 

Assuming on a 4501?

Best Regards, Phil
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phil4501
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« Reply #2 on: May 21, 2006, 08:23:29 AM »

I was refering to the battery banks, inverter/charging systems, fridge, alternator, starter but not necessarily the headlamps, marker lights or interior lights.

I am redoing the electrical ststem right know thus reading alot about the subject. I am convinced that if I had a 24v bus, I would keep it and continue with it for the house batteries and solar, (if and when I add solar). It seems as though I should consider 24v if it is truly better. However, in all my research, I have yet to see a recomendation to do this. I have never even seen the subject brought up. As passionate as people are on the subject, I would think it would have been mentioned if it was sane to do so.
« Last Edit: May 21, 2006, 08:35:36 AM by phil4501 » Logged
Chuck Newman
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« Reply #3 on: May 21, 2006, 08:57:43 AM »

Phil,

24vdc systems have advantages over 12vdc systems.  Smaller wire, less voltage drop for a length of wire, less power loss (voltage x current) due to higher than normal resistance in connectors, etc.  This is why most (certainly not all) busses and heavy mortoized equipment have used 24vdc systems for decades.  And their is a move afoot in Detroit to start making cars/pickups with 24vdc due to the increased amount of electronic devices being added to vehicles.  The only real down side is you need twice the number of 12 volt batteries.

That said, if you have a 12vdc bus (or anything else), it really won't be worth the time, effort, and money to convert from 12vdc to 24vdc.  In fact, it would be to your advantage to leave it 12vdc.  An example of why using my situation:  My bus is an MCI with 24vdc system.  Batteries, alternator, lamp bulbs, instruments, engine computer, etc. all running on 24vdc.   And most RV/Marine devices in the world (lights, fans, refers, furnaces, hot water heaters, CB's, radios, CD players, TV's, water pumps, etc. etc.), all run at 12vdc. 

So I my case I had the option of keeping the 24vdc system in place, using one existing high amp alternator and charging two separate set of 24vdc batteries (house batteries and engine batteries;  and converting to 12vdc only where necessary for specific 12vdc lights/appliances.  OR do as a few have and install a separate 12vdc alternator, 12vdc house batteries, etc.

The point here is most of the electrical items you will add to your 12vdc bus require 12vdc to operate.  You have the advantage over us 24vdc guys that you don't have to consider any of the 24vdc/12vdc issues we do, and the various methods used to accomodate the difference.  I your case, you don't have to worry about two different DC levels, conversions, etc.

Yes, 24vdc have many advantages over 12vdc systems, but in your case replaceing the alternator, instruments, relays, solenoids, bulbs, etc. just to have a higher voltage system then have to reconvert much of it back down to 12vdc to run appliances, etc. is not a logical step in the bus conversion process.

Chuck Newman
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« Reply #4 on: May 21, 2006, 09:55:44 AM »

Phil,  Everyone has a opinion, so here's mine-I'm not disagreeing with anyone else,only sharing my thoughts on the subject as someone who has the system in place.

[b]I am refeering to the house battery bank and charging system only.
I would not alter a 12V coach chassis system
.[/b][/color]

If you want large inverter capacity, a seperate 24Volt engine driven atlernator/generator to power the inverter and 24volt house bank would at least be worth consideration.

The biggest  advantage of 24V vs 12V is realized if you want to use a large inverter. I use a Trace SW4024 for inverting/battery charging.

With the Trace, you can use 120 volt AC items instead of 12V DC items and eliminate much of the 12volt needs. 120 AC lighting is so much better.

[u]You can, of course, use a 12volt inverter and do the same thing, just with less power. The deciding factor is how much oomph you need, and consider the amount of  difference between what you can do with 12volts vs what 24Volts will do.[/u]

A Vanner Equalizer to connected to my house battery bank provides my 12V stuff. (I use 8 golf cart batteries for the house bank)
the 12V items work flawlessly in this system.

I use a 24V constant duty solenoid to connect  the house batteries to the coach electrical system to recharge from the bus 24V generator. The relay terminal of the bus generator signals the relay(solenoid) to connect/disconnect the house batteries from the coach system.
I use the evaparator motor solenoid that I scavenged from my coach after the OTR a/c was removed.

I beleive this is the most common setup for guys with 24Volt coaches.

In addition, I have a 4 panel set of solars, with a Trace 3 stage regulator, for the house bank.

MCI type 24v alternators/generators could be mounted as a second charging source on most coaches, you would just have to research what would need to happen in your situation.

« Last Edit: May 21, 2006, 10:51:09 AM by ChuckMC8 » Logged

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« Reply #5 on: May 21, 2006, 12:00:16 PM »

I also use a 4024 [computer controlled] from the on-board bus computer and a 24vdc continuous duty solenoid to connect my House banks [8 8d's] to the Bus bank[2 8d's] as and when needed.

I run an all electric coach, that is to say that I have no propane and all 110vac lights, hot water and appliances. This is backed up by a 12,500 watt Onan Quiet Diesel Genset.

Solar panels is my next planned addition.


Steve
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« Reply #6 on: May 21, 2006, 08:30:09 PM »

Steve, I am totally impressed.    Smiley  Cool

Nice layout!  Gives me something to think about for sure.

Best Regards, Phil
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phil4501
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« Reply #7 on: May 22, 2006, 08:49:00 AM »

Thanks for the great replies

Can additional chargers be add to the 4024 that are compatible to the point where I can add additional 110v charging while still utilizing the charge feature that is built in the inverter/charger?

I have a 6 golf carts in 12v temp system now. Coach is all electric, set up to be plugged in or have the 12KW air cooled deisel gen running all the time. Every thing is 110v except some interior lights and the 12v feature of the 2 way 12v/v rv fridge the probably won't stay.

When I get an idea of our electrical needs and wants I will step up to better system. I was leaning towards 12v with an RS3000 and 8 agm 8d's. I have to have agms because of thier location, so to help justify the expense of these I was hoping to fast charge them with multiple ac charge sources thus squeezing all I can out the the generator run time. I am hoping not to have to upgrade to a watercooled gen and keep any solar array to a minimum.
. It is my understanding that the charger feature of the RS3000 will not work with  other chargers so I am trying to start with a clean sheet of paper.

The coach will used for boondocking almost every trip. We are never plugged in.
« Last Edit: May 22, 2006, 08:52:46 AM by phil4501 » Logged
DrivingMissLazy
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« Reply #8 on: May 22, 2006, 09:11:40 AM »

Thanks for the great replies

Can additional chargers be add to the 4024 that are compatible to the point where I can add additional 110v charging while still utilizing the charge feature that is built in the inverter/charger?

I have a 6 golf carts in 12v temp system now. Coach is all electric, set up to be plugged in or have the 12KW air cooled deisel gen running all the time. Every thing is 110v except some interior lights and the 12v feature of the 2 way 12v/v rv fridge the probably won't stay.

When I get an idea of our electrical needs and wants I will step up to better system. I was leaning towards 12v with an RS3000 and 8 agm 8d's. I have to have agms because of thier location, so to help justify the expense of these I was hoping to fast charge them with multiple ac charge sources thus squeezing all I can out the the generator run time. I am hoping not to have to upgrade to a watercooled gen and keep any solar array to a minimum.
. It is my understanding that the charger feature of the RS3000 will not work with  other chargers so I am trying to start with a clean sheet of paper.

The coach will used for boondocking almost every trip. We are never plugged in.

Unfortunately you can only charge batteries at a limited amount of amps or you will overheat/boil them. I seriously doubt if you will ever exceed the charging capacity of the 4024.

It is difficult to get two battery chargers to share load equally, unless you have some method of them talking to each other, and I have never seen a device like that.
Richard
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« Reply #9 on: May 22, 2006, 09:34:25 AM »

Steve,

I have a 12.5 Onan quiet diesel in my MC9 also, but have only installed it on a slide so far.  I have been trying to figure out the best way to run the exhaust so I can disconnect it easily, because I am running the exhaust through the roof instead of out the bottom.  I was curious how you have you exhaust set up?  Any suggestions?  Any pics?  Thanks in advance.   



I also use a 4024 [computer controlled] from the on-board bus computer and a 24vdc continuous duty solenoid to connect my House banks [8 8d's] to the Bus bank[2 8d's] as and when needed.

I run an all electric coach, that is to say that I have no propane and all 110vac lights, hot water and appliances. This is backed up by a 12,500 watt Onan Quiet Diesel Genset.

Solar panels is my next planned addition.


Steve

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BJW
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« Reply #10 on: May 22, 2006, 10:03:47 AM »


The coach will used for boondocking almost every trip. We are never plugged in.


If "Boondocking" or Dry Camping, is your way to go, then electrical storage is the key... To put it simple for others interested in this way of camping, you will need as much electrical storage as you can ie: battery banks, Then you will need a system to replenish what you take out of those batteries, by way of a generator, wind or solar system [or combination thereof]

This is such a variable thing and depends totally on ones own usage, If your sole electrical usage is small, then a small system will do, however, if you are like most, then both your storage capacity and your replenishment system both increases to match, as I'm sure you already know.

There is a place called Quartzite, in Arizona, where boondocking and the use of solar replenishment of your electrical storage [battery charging] is used extensively. These guys that stay in the desert down there are, for the most part, tried and true experts in what works for them.

I'm sure if you did a Google that included Quartzite AZ, Solar, RV, you will eventually hit upon those that have a great deal of experience and knowledge. Every year [in the winter] a large open air market pops up with solar power vendors and installers, most are very good at what they do.

Quartzite has a population around 1,500 but swells, some say into the millions during doondocking season.

This is the largest gathering of Boondockers that I know about.

Steve
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« Reply #11 on: May 22, 2006, 10:27:25 AM »


Steve,

I have a 12.5 Onan quiet diesel in my MC9 also, but have only installed it on a slide so far. I have been trying to figure out the best way to run the exhaust so I can disconnect it easily, because I am running the exhaust through the roof instead of out the bottom. I was curious how you have you exhaust set up? Any suggestions? Any pics? Thanks in advance.


BJW... Hi

I routed my exhaust down through my bed slide that the genny sits on, then brought it out the side under the bed slide but over the floor of the luggage bay to a point just past the outer skin of the luggage bay door. I cut a hole in the bay door for the exhaust to clear when the door is closed. This allows me to open and close the bay door and slide out the genny for servicing. The fuel lines, power cables and exhaust all come out with the genny on the bed slide.

I have a photo of it someplace; I'll try and find it and post here for you later.

I had also considered using flexible exhaust pipe initially, but didn't like the system. I have heard that some places require the venting to be above the roof line, but I have never run into that at any of the places I have been. I don't believe it to be a law, just certain parks policies. I noticed one guy used a temporary extension pipe to route his exhaust up the side of his bus to clear his roof line to appease the park rules. Some places also limit the use of generators during certain times of the day or night.

I guess it depends where you go and how much you may bother others around you.

Steve


Sorry Phil for getting a little off-topic

* BJW - Here is the only photo I have - look in the lower right corner for the exhaust and the upper right corner for the pass-through-hole in the bay door.
« Last Edit: May 23, 2006, 05:14:04 AM by El Soņador™ » Logged
Nick Badame Refrig/ACC
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« Reply #12 on: May 22, 2006, 12:18:51 PM »

How are you STEVE,

Quick Question, I have the same gen as you, And I orrigenally wanted a slide but nixed it because of the bottom intake and exhaust.

I had to install 2 12v automotive radiator fans in the exhaust holes under the bus to disapate the heat.

How did you accomplish that with your slide??

Thanks
Nick-
« Last Edit: May 22, 2006, 12:24:10 PM by Nick Badame Refrig. Co. » Logged

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« Reply #13 on: May 22, 2006, 01:07:36 PM »

It's only a distant memory but, it seems to me that I have seen a vintage Bluebird with the front slide out generator.  The exhaust would disconnect when it was pulled out.  There was a funnel like arrangement that would guide the connection as it was pushed back in. This was probably in the seventies.

I can't imagine how it was kept leak tight or kept from seizing up over time.

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« Reply #14 on: May 22, 2006, 01:10:21 PM »


How are you STEVE,

Quick Question, I have the same gen as you, And I orrigenally wanted a slide but nixed it because of the bottom intake and exhaust. I had to install 2 12v automotive radiator fans in the exhaust holes under the bus to disapate the heat.

How did you accomplish that with your slide??

Thanks Nick-


Hey Nick...

Poor Phil seems to be getting his thread hijacked here... hope he dosen't mind...

I used scuppers [a marine system] cut into the floor of the luggage bay... One forward and one aft, both facing backwards... This scoops up intake air, while the other creates a low pressure within the bay, exhausting the air. You can find a smaller version of this located in the bus battery bay floor to vent out unwanted gasses, at least on the MC-9's. There seems to be enough fan circulation from the genset to do this even while stopped. I guess in extreme conditions, while parked, I could open the bay doors and even operate the genset with the bedslide in the extended position, But I have never had to resort to that. I did plan on converting the skin of the bay door to a fully vented screened skin, similar to the Bus A/C condenser compartment door, but have not had any problems with overheating so far.

Steve
« Last Edit: May 22, 2006, 01:16:58 PM by El Soņador™ » Logged
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